What Happens When Water Gets into a Fuel Tank?

by Don Bowman

How the Water Gets in the Tank

Water in the fuel in any quantity is not a normal occurrence. It should be investigated as to the origin, such as a rusty fuel tank or bad top fuel pump seal. The only other answer would be that it was acquired from a recent fueling. Service stations have the duty to keep track of the amount of fuel in the tanks to compare this figure to the records of sales. This accomplishes three goals--confirms the records, checks for the depth of the water in the fuel tank and indicates if the tank has sprung a fuel leak into the ground, which is serious business and must be dealt with immediately.

Service stations are vulnerable to getting water into their tanks. If it is raining when they are receiving fuel, water will run down into the tanks. Also the same thing applies when the employees dip the tanks at the end of their shift to confirm the sales and the money they are responsible for. If it is raining, they still want to go home so they will dip the tanks regardless. When the tank is dipped, the person dipping or measuring the amount of fuel in the tank must apply a paste specifically designed to turn color. This shows whether there is water in the tank or not. If this step is eliminated or the tank is drained to low (down to the water before it is refilled), water will be pumped into the gas tank.

Water in the tank can also come from condensation from quickly changing weather from a temperature and humidity standpoint. This however is usually negligible. There is a better possibility of collecting water in a fuel tank when the vehicle is stored in a non-air-conditioned atmosphere in severe temperature swings.

What Happens

Water in the fuel tank has no positive aspects--only negative. It will rust the interior of the fuel tank, clog up lines, foul the fuel filter, ruin the electric fuel pump if it is submerged in it and is catastrophic to fuel injectors if sufficient water is in the tank and makes it to the injectors. The injector's pintle is the size of a hypodermic needle and it moves at an incredible speed. The pintle is lubricated by the fuel. When water hits the injectors it takes little time to destroy them.

Removing Water from the Tank

If water is suspected due to reduced engine performance and idle characteristics, the fuel system should be opened and fuel drained into a glass container. If there is water, it will go to the bottom of the container and seen clearly. The fuel will float on the top of the water. If water is detected in any amount, such as filling a drinking glass, then the fuel tank should be drained. When refilled, add a container of Dry Gas into the tank. Dry Gas mixes with the water molecules and allows the water to burn off. This is only affective if there is only a small amount of water in the tank.

About the Author

Don Bowman has been writing for various websites and several online magazines since 2008. He has owned an auto service facility since 1982 and has over 45 years of technical experience as a master ASE tech. Bowman has a business degree from Pennsylvania State University and was an officer in the U.S. Army (aircraft maintenance officer, pilot, six Air Medal awards, two tours Vietnam).